Preheat the oven to 350 and butter a 9-inch round cake pan.
In a large bowl, sift flour, baking powder, soda and salt. In a small bowl, mix cider vinegar and 3 tbsp milk and in another bowl, mix 2 tbsp milk, molasses and eggs. Mix both of the wet mixes together and add to the dry ingredients until just combined. Add the butter and toss the blueberries with the sugar (optional) and flour in another bowl, then fold into the batter.
Pour into the prepared pan and bake for 25-30 minutes. A toothpick should come out clean when it’s done. It was at this point that the top was done but not quite inside so I placed foil over the top to prevent burning. I cooked it another 10 minutes and it was perfect, except for the small amount of top that came off with the foil-oops. Let it cool and dust with powdered sugar and top with whipping cream (optional) when serving.